THE MICROBIOLOGY OF THE ATMOSPHERE 



Sreeramulu (1958^) used a Hirst trap at 70 ft. above sea-level on a 

 voyage in the Mediterranean in October and November, 1956. At 5 

 to 50 miles from land he found an average of 56-4 fungus spores and i-6 

 pollen grains per cubic metre. In Malta Harbour the concentrations v^ere 

 121 and 1 2 per cubic metre, respectively. At sea, Cladosporium predominated 

 with 16 spores per cubic metre, followed by smuts with 5 per cubic metre, 

 and coloured basidiospores with 7 per cubic metre. Also of interest was 

 the occurrence of spores oi Helminthosporium^ Alternaria, Torula herbarum^ 

 Nigrospora^ Curvularia, and Epicoccum^ as well as hyphal fragments. 



Pollen in marine air must come from land plants; the mould spora is 

 more characteristic of above-ground sources than of the soil; the bacteria, 

 however, may well come largely from sea water and soil. 



The Air of Polar Regions 



The air of polar regions seems to be still purer than that over the sea. 

 Levin (1899), who aspirated air through powdered-sugar filters, obtained 

 only three bacterial colonies and a few moulds in a total of 20 cubic metres 

 of air sampled at various points in Spitsbergen (Svalbard). 



During 2 years on an island near Graham Land, Antarctica, Ekelof 

 (1907) exposed Petri dishes at intervals; 40 per cent of them grew bacteria, 

 which he thought came from the soil. On the average, one colony arose 

 per 2-hours exposure. 



Pirie (191 2) exposed Petri dishes in the 'crow's nest' of the Scotia 

 in the Weddell Sea, Antarctica, during the summer of 1903, for as long as 

 20 hours, and also on a glacier at Scotia Bay during winter; they all 

 remained sterile. E. Hesse (191 4) exposed Petri dishes while at sea south 

 of Spitsbergen and also found the air to be almost sterile. 



Darling & Siple (1941) exposed jars and dishes of media in remote 

 places in Marie Byrd Land, Antarctica, and from their isolations identi- 

 fied: Achromobacter delicatulum^ A. liquidum^ Bacillus albolactis, B.fusi- 

 fonnis, B. mesentericus, B. subtilis, and B. tumescens. They concluded that, 

 although some bacteria had been brought to Antarctica by man and 

 migrating animals, the vast majority must have come as atmospheric 

 dust in subsiding air. 



Recent work in the Arctic has demonstrated a fair range but sparse 

 'population' of microbes to be present in the air in summer near ground- 

 and sea-level in various parts of those vast regions. Polunin (1954, 1955) 

 organized the exposure of sticky slides at several points ranging eastwards 

 from Point Barrow, Alaska, to Spitsbergen, in 1950, and found a consider- 

 able variety of pollen grains and 'probable moss spores' at each station. 

 Remarkably enough the pollen grains caught most plentifully through most 

 of that summer in Spitsbergen were of Pinus — several hundreds of kilo- 

 metres from their nearest possible source. In 1954 Polunin (1955^?) was 

 responsible for the exposure of sticky slides (cf. Polunin, i960) off the 



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